Some devices fail to cope in disastrous ways with the small command turn-around times enabled by in-kernel device drivers.
Introduce per-client throttling of transfers to avoid these issues. Signed-off-by: Andrew Jeffery <[email protected]> --- drivers/i2c/i2c-core-base.c | 8 +- drivers/i2c/i2c-core-smbus.c | 149 ++++++++++++++++++++++++++++------- drivers/i2c/i2c-core.h | 22 ++++++ include/linux/i2c.h | 3 + 4 files changed, 151 insertions(+), 31 deletions(-) diff --git a/drivers/i2c/i2c-core-base.c b/drivers/i2c/i2c-core-base.c index 5ec082e2039d..d5a519bcadf9 100644 --- a/drivers/i2c/i2c-core-base.c +++ b/drivers/i2c/i2c-core-base.c @@ -867,13 +867,17 @@ int i2c_dev_irq_from_resources(const struct resource *resources, struct i2c_client * i2c_new_client_device(struct i2c_adapter *adap, struct i2c_board_info const *info) { + struct i2c_client_priv *priv; struct i2c_client *client; int status; - client = kzalloc(sizeof *client, GFP_KERNEL); - if (!client) + priv = kzalloc(sizeof(*priv), GFP_KERNEL); + if (!priv) return ERR_PTR(-ENOMEM); + mutex_init(&priv->throttle_lock); + client = &priv->client; + client->adapter = adap; client->dev.platform_data = info->platform_data; diff --git a/drivers/i2c/i2c-core-smbus.c b/drivers/i2c/i2c-core-smbus.c index f5c9787992e9..4a9692a37e1e 100644 --- a/drivers/i2c/i2c-core-smbus.c +++ b/drivers/i2c/i2c-core-smbus.c @@ -10,6 +10,7 @@ * SMBus 2.0 support by Mark Studebaker <[email protected]> and * Jean Delvare <[email protected]> */ +#include <linux/delay.h> #include <linux/device.h> #include <linux/err.h> #include <linux/i2c.h> @@ -21,6 +22,9 @@ #define CREATE_TRACE_POINTS #include <trace/events/smbus.h> +static s32 i2c_smbus_throttle_xfer(const struct i2c_client *client, + char read_write, u8 command, int protocol, + union i2c_smbus_data *data); /* The SMBus parts */ @@ -95,9 +99,9 @@ s32 i2c_smbus_read_byte(const struct i2c_client *client) union i2c_smbus_data data; int status; - status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_READ, 0, - I2C_SMBUS_BYTE, &data); + status = i2c_smbus_throttle_xfer(client, I2C_SMBUS_READ, 0, + I2C_SMBUS_BYTE, &data); + return (status < 0) ? status : data.byte; } EXPORT_SYMBOL(i2c_smbus_read_byte); @@ -112,8 +116,8 @@ EXPORT_SYMBOL(i2c_smbus_read_byte); */ s32 i2c_smbus_write_byte(const struct i2c_client *client, u8 value) { - return i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_WRITE, value, I2C_SMBUS_BYTE, NULL); + return i2c_smbus_throttle_xfer(client, I2C_SMBUS_WRITE, value, + I2C_SMBUS_BYTE, NULL); } EXPORT_SYMBOL(i2c_smbus_write_byte); @@ -130,9 +134,9 @@ s32 i2c_smbus_read_byte_data(const struct i2c_client *client, u8 command) union i2c_smbus_data data; int status; - status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_READ, command, - I2C_SMBUS_BYTE_DATA, &data); + status = i2c_smbus_throttle_xfer(client, I2C_SMBUS_READ, command, + I2C_SMBUS_BYTE_DATA, &data); + return (status < 0) ? status : data.byte; } EXPORT_SYMBOL(i2c_smbus_read_byte_data); @@ -150,10 +154,10 @@ s32 i2c_smbus_write_byte_data(const struct i2c_client *client, u8 command, u8 value) { union i2c_smbus_data data; + data.byte = value; - return i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_WRITE, command, - I2C_SMBUS_BYTE_DATA, &data); + return i2c_smbus_throttle_xfer(client, I2C_SMBUS_WRITE, command, + I2C_SMBUS_BYTE_DATA, &data); } EXPORT_SYMBOL(i2c_smbus_write_byte_data); @@ -170,9 +174,9 @@ s32 i2c_smbus_read_word_data(const struct i2c_client *client, u8 command) union i2c_smbus_data data; int status; - status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_READ, command, - I2C_SMBUS_WORD_DATA, &data); + status = i2c_smbus_throttle_xfer(client, I2C_SMBUS_READ, command, + I2C_SMBUS_WORD_DATA, &data); + return (status < 0) ? status : data.word; } EXPORT_SYMBOL(i2c_smbus_read_word_data); @@ -190,10 +194,10 @@ s32 i2c_smbus_write_word_data(const struct i2c_client *client, u8 command, u16 value) { union i2c_smbus_data data; + data.word = value; - return i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_WRITE, command, - I2C_SMBUS_WORD_DATA, &data); + return i2c_smbus_throttle_xfer(client, I2C_SMBUS_WRITE, command, + I2C_SMBUS_WORD_DATA, &data); } EXPORT_SYMBOL(i2c_smbus_write_word_data); @@ -218,9 +222,9 @@ s32 i2c_smbus_read_block_data(const struct i2c_client *client, u8 command, union i2c_smbus_data data; int status; - status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_READ, command, - I2C_SMBUS_BLOCK_DATA, &data); + status = i2c_smbus_throttle_xfer(client, I2C_SMBUS_READ, command, + I2C_SMBUS_BLOCK_DATA, &data); + if (status) return status; @@ -248,9 +252,8 @@ s32 i2c_smbus_write_block_data(const struct i2c_client *client, u8 command, length = I2C_SMBUS_BLOCK_MAX; data.block[0] = length; memcpy(&data.block[1], values, length); - return i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_WRITE, command, - I2C_SMBUS_BLOCK_DATA, &data); + return i2c_smbus_throttle_xfer(client, I2C_SMBUS_WRITE, command, + I2C_SMBUS_BLOCK_DATA, &data); } EXPORT_SYMBOL(i2c_smbus_write_block_data); @@ -264,9 +267,9 @@ s32 i2c_smbus_read_i2c_block_data(const struct i2c_client *client, u8 command, if (length > I2C_SMBUS_BLOCK_MAX) length = I2C_SMBUS_BLOCK_MAX; data.block[0] = length; - status = i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_READ, command, - I2C_SMBUS_I2C_BLOCK_DATA, &data); + status = i2c_smbus_throttle_xfer(client, I2C_SMBUS_READ, command, + I2C_SMBUS_I2C_BLOCK_DATA, &data); + if (status < 0) return status; @@ -284,9 +287,8 @@ s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, u8 command, length = I2C_SMBUS_BLOCK_MAX; data.block[0] = length; memcpy(data.block + 1, values, length); - return i2c_smbus_xfer(client->adapter, client->addr, client->flags, - I2C_SMBUS_WRITE, command, - I2C_SMBUS_I2C_BLOCK_DATA, &data); + return i2c_smbus_throttle_xfer(client, I2C_SMBUS_WRITE, command, + I2C_SMBUS_I2C_BLOCK_DATA, &data); } EXPORT_SYMBOL(i2c_smbus_write_i2c_block_data); @@ -547,6 +549,71 @@ s32 i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, } EXPORT_SYMBOL(i2c_smbus_xfer); +static int i2c_smbus_throttle_enter(const struct i2c_client *client) + __acquires(&priv->throttle_lock) +{ + struct i2c_client_priv *priv; + ktime_t earliest; + int rc; + + priv = to_i2c_client_priv(client); + + if (i2c_in_atomic_xfer_mode()) { + if (!mutex_trylock(&priv->throttle_lock)) + return -EAGAIN; + } else { + rc = mutex_lock_interruptible(&priv->throttle_lock); + if (rc) + return rc; + } + earliest = ktime_add_us(priv->last, priv->delay_us); + + if (priv->delay_us && ktime_before(ktime_get(), earliest)) { + if (i2c_in_atomic_xfer_mode()) { + mutex_unlock(&priv->throttle_lock); + return -EAGAIN; + } + + usleep_range(priv->delay_us, 2 * priv->delay_us); + } + + return 0; +} + +static void i2c_smbus_throttle_exit(const struct i2c_client *client) + __releases(&priv->throttle_lock) +{ + struct i2c_client_priv *priv; + + priv = to_i2c_client_priv(client); + + if (priv->delay_us) + priv->last = ktime_get(); + mutex_unlock(&priv->throttle_lock); +} + +static s32 i2c_smbus_throttle_xfer(const struct i2c_client *client, + char read_write, u8 command, int protocol, + union i2c_smbus_data *data) +{ + s32 res; + + res = i2c_smbus_throttle_enter(client); + if (res) + return res; + + res = __i2c_lock_bus_helper(client->adapter); + if (!res) + res = __i2c_smbus_xfer(client->adapter, client->addr, + client->flags, read_write, command, + protocol, data); + i2c_unlock_bus(client->adapter, I2C_LOCK_SEGMENT); + + i2c_smbus_throttle_exit(client); + + return res; +} + s32 __i2c_smbus_xfer(struct i2c_adapter *adapter, u16 addr, unsigned short flags, char read_write, u8 command, int protocol, union i2c_smbus_data *data) @@ -715,3 +782,27 @@ int of_i2c_setup_smbus_alert(struct i2c_adapter *adapter) } EXPORT_SYMBOL_GPL(of_i2c_setup_smbus_alert); #endif + +int i2c_smbus_throttle_client(struct i2c_client *client, + unsigned long delay_us) +{ + struct i2c_client_priv *priv; + int rc; + + priv = to_i2c_client_priv(client); + + if (i2c_in_atomic_xfer_mode()) { + if (!mutex_trylock(&priv->throttle_lock)) + return -EAGAIN; + } else { + rc = mutex_lock_interruptible(&priv->throttle_lock); + if (rc) + return rc; + } + priv->delay_us = delay_us; + priv->last = ktime_get(); + mutex_unlock(&priv->throttle_lock); + + return 0; +} +EXPORT_SYMBOL_GPL(i2c_smbus_throttle_client); diff --git a/drivers/i2c/i2c-core.h b/drivers/i2c/i2c-core.h index 8ce261167a2d..c763c6c431f9 100644 --- a/drivers/i2c/i2c-core.h +++ b/drivers/i2c/i2c-core.h @@ -4,6 +4,28 @@ */ #include <linux/rwsem.h> +#include <linux/i2c.h> +#include <linux/timekeeping.h> +#include <linux/kernel.h> +#include <linux/mutex.h> + +struct i2c_client_priv { + struct i2c_client client; + + /* + * Per-client access throttling, described in terms of microsecond + * delay between the end of the nth transfer and the start of the + * (n+1)th transfer. Used to manage devices which respond poorly to + * rapid back-to-back commands. + * + * Do it in a wrapper struct to preserve const-ness of the i2c_smbus_* + * interfaces. + */ + struct mutex throttle_lock; + unsigned long delay_us; + ktime_t last; +}; +#define to_i2c_client_priv(c) container_of(c, struct i2c_client_priv, client) struct i2c_devinfo { struct list_head list; diff --git a/include/linux/i2c.h b/include/linux/i2c.h index fc55ea41d323..adc91587d7fa 100644 --- a/include/linux/i2c.h +++ b/include/linux/i2c.h @@ -181,8 +181,11 @@ s32 i2c_smbus_write_i2c_block_data(const struct i2c_client *client, s32 i2c_smbus_read_i2c_block_data_or_emulated(const struct i2c_client *client, u8 command, u8 length, u8 *values); +int i2c_smbus_throttle_client(struct i2c_client *client, + unsigned long delay_us); int i2c_get_device_id(const struct i2c_client *client, struct i2c_device_identity *id); + #endif /* I2C */ /** -- 2.25.1
